1. Field of the Invention
The present invention relates to an organic electroluminescence device (organic EL device) and a display that use a naphthacene derivative and a compound having a pyrromethene skeleton or a metal complex of the compound together.
2. Description of Related Art
Organic electroluminescence (EL) devices have been known. Organic EL devices formed from organic materials have been vigorously studied since a report on a low voltage-driven organic EL device formed by laminating layers was made by C. W. Tang et al. of Eastman Kodak Company (see Document 1: Applied Physics Letters, vol. 51, page 913, by C. W. Tang and S. A. Vanslyke, 1987).
Known examples of an emitting material used for an organic EL device are a chelate complex such as a tris(8-quinolinol)aluminum (Alq) complex, a coumarin complex, a tetraphenylbutadiene derivative, a bisstyrylarylene derivative, an oxadiazole derivative or the like. These emitting materials, which have been reported to emit blue to red light in a visible region, are expected to be applied to color-display devices (e.g., Document 2: JP-A-08-239655, Document 3: JP-A-07-138561, Document 4: JP-A-03-200889 and the like). However, luminous efficiency and lifetime of such a device has been so insufficient that the device has not been practically applicable. While a full color display requires three primary colors of blue, green and red, among them, a red-emitting device with high efficiency has been demanded.
For instance, Document 5 (JP-A-08-311442) has recently disclosed a red-emitting device whose emitting layer is added with a naphthacene derivative or a pentacene derivative. However, although the red-emitting device is excellent in purity of red color, the red-emitting device requires voltage of 11V to be applied, and time lapsed until the luminescent intensity decreases to half is approximately 150 hours, i.e., the performance of the device is insufficient. Document 6 (JP-A-03-162481) discloses a device whose emitting layer is added with a dicyanomethylene (DCM)-based compound. However, the device exhibits insufficient purity of red color. Document 7 (JP-A-2001-81451) discloses a red-emitting device whose emitting layer is added with an amine-based aromatic compound. However, although the emitting device exhibits excellent CIE (Commission Internationale d'Eclairage) chromaticity (0.64, 0.33) and chromatic purity, the device requires high voltage for driving. Document 8 (WO/01/23497) and Document 9 (JP-A-2003-40845) disclose devices in which an amine-based aromatic compound and an Alq compound are used for the emitting layer. However, although emitting red light, the device exhibits low efficiency and short lifetime.
Document 10 (JP-A-2003-81924) discloses devices in which an amine-based aromatic compound and DPVDPAN are used for the emitting layer. However, high-efficient one of the devices emits orange light while red-emitting one of the devices exhibits low efficiency.
Document 11 (JP-A-2001-307885) discloses a device in which a dicyanoanthracene derivative and an indenoperylene derivative are used for the emitting layer while a metal complex is used for the electron transporting layer. However, the device emits light of red orange color.
Document 12 (JP-A-2003-338377) discloses a device in which a fluoranthene derivative and an indenoperylene derivative are used for the emitting layer while a fluoranthene derivative is used for the electron transporting layer. However, the device does not exhibit practically-applicable efficiency.